Obstructive shock caused by right atrial thrombosis secondary to malignant pheochromocytoma in a dog

Abstract

Background Obstructive shock can be caused by any lesion leading to extraluminal compression or intraluminal occlusion of the cardiac chambers or major vessels. Case Report A 12‐year‐old, male castrated, Border Collie cross dog presented to a veterinary teaching hospital for collapse. A physical examination revealed severe vasoconstrictive shock and abdominal distension. Abnormalities on blood tests were consistent with systemic hypoperfusion. Cardiac underfilling, hepatomegaly with distended vasculature and ascites were identified by focused ultrasonography, raising suspicion of obstructive shock. This was supported by the radiographic findings of microcardia and a distended caudal vena cava (CVC). There was transient response to fluid therapy for blood volume expansion. Repeat focused ultrasonography during rapid intravenous fluid administration identified a right intra‐atrial mass, assessed as likely to be causing obstruction of venous return. The dog was humanely euthanased given the guarded prognosis. At postmortem evaluation, a malignant pheochromocytoma in the left adrenal gland with tumour thrombus extending to the tricuspid valve through the CVC was found. The extensive thrombus caused the obstructive shock in this case. Metastasis in a peripheral lymph node and neoplastic emboli in the heart and lungs were also visible at the histopathological evaluation. Conclusion To the best of authors' knowledge, this is the first report of severe obstructive shock secondary to extension of caval tumour thrombus into the right atrium in a dog with malignant pheochromocytoma. Tumour thrombus from a malignant pheochromocytoma should be included as a differential diagnosis of obstructive shock, with or without a visible right intra‐atrial mass, in dogs. Serial focused ultrasonography during intravenous fluid administration can aid diagnosis.

Sudden death caused by pulmonary tumor embolism in a dog

“…However, emboli release from these neoplastic thrombi is generally not a feature of these tumors (BARRERA et al, 2013;ROBVEILLE et al, 2020). In fact, some of these neoplasms form neoplastic thrombi large enough to reach the heart, and even in these cases, emboli are not reported (ROBVEILLE et al, 2020). The adrenal tumor described in the present case had large friable areas of coagulation necrosis, which may have contributed to thrombus fragmentation, facilitating emboli release.…”

“…When large enough, emboli may be visible in imaging exams, which can contribute to a clinical suspicion of TE (TAKAHASHI et al, 2008). Probably due to their anatomic proximity to the caudal vena cava, it is not uncommon for canine malignant adrenal tumors to invade the vascular wall and form an intravascular neoplastic thrombus (BARRERA et al, 2013, ROBVEILLE et al, 2020. In a systematic study on dogs undergoing adrenalectomy to treat adrenal gland tumors, approximately 19% of the malignant neoplasms invaded the adjacent vena cava (BARRERA et al, 2013).…”

“…In a systematic study on dogs undergoing adrenalectomy to treat adrenal gland tumors, approximately 19% of the malignant neoplasms invaded the adjacent vena cava (BARRERA et al, 2013). However, emboli release from these neoplastic thrombi is generally not a feature of these tumors (BARRERA et al, 2013;ROBVEILLE et al, 2020). In fact, some of these neoplasms form neoplastic thrombi large enough to reach the heart, and even in these cases, emboli are not reported (ROBVEILLE et al, 2020).…”

“…Pheochromocytomas are the most common neoplasms in the adrenal medulla of dogs, and generally develop on middle-aged to older animals, with no apparent gender or breed predisposition (ROSOL & MEUTEN, 2017). Many of them are clinically silent; however, these neoplasms may be associated with clinical signs, either due to vena cava invasion/metastases or due to hormonal production (ROSOL & MEUTEN, 2017;ROBVEILLE et al, 2020). If severe enough to occlude the vena cava, invasive tumors may lead to impaired venous return, which can contribute to hindlimb edema or even obstructive shock (BARRERA et al, 2013;ROBVEILLE et al, 2020).…”

Right atrial thrombus formation in a dog after successful electrical cardioversion for atrial fibrillation

“…5 Echocardiographic detection of a right atrial mass in a dog is commonly associated with malignant neoplasia, with hemangiosarcoma being the most prevalent tumor type. [12][13][14] We describe a dog that was diagnosed with a right atrial mass on echocardiography 2 weeks after successful electrical cardioversion because of acute atrial fibrillation. Anticoagulation treatment resulted in complete resolution of the right atrial mass within 2 months.…”